Atomic Structure and Electron Configuration

What do electron configurations describe?

• The location of electrons around the nucleus of an atom

• The number of protons in an atom

• The mass of an atom

• The size of an atom

Answer explanation

Electron configurations describe the arrangement of electrons around the nucleus of an atom. This is the correct answer because it accurately reflects the concept of electron configurations, which is the distribution of electrons of an atom or molecule in atomic or molecular orbitals. The other options, such as the number of protons, the mass, or the size of an atom, are not what electron configurations describe.

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What is the electron configuration of lithium?

• 1s²2s¹

• 1s²2s²2p⁶3s²

• 1s²2s²2p⁶3s¹

• 1s²2s²2p⁶

Answer explanation

The electron configuration of an atom represents the distribution of electrons in its atomic orbitals. For lithium, which has an atomic number of 3, the electron configuration is 1s²2s¹. This means there are 2 electrons in the 1s subshell and 1 electron in the 2s subshell. The other options represent configurations for different elements, not lithium.

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Which subshell does lithium's third electron go to?

• 1s

• 2s

• 2p

• 3s

Answer explanation

Lithium's third electron goes to the 2s subshell. The electron configuration of lithium is 1s² 2s¹, which means that the first two electrons fill the 1s subshell, and the third electron goes to the 2s subshell.

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How many electrons does the 1s subshell of lithium have?

• 0

• 1

• 2

• 3

Answer explanation

The 1s subshell of lithium has 2 electrons. Lithium has an atomic number of 3, which means it has 3 electrons in total. The electron configuration is 1s²2s¹, with 2 electrons filling the 1s subshell and 1 electron in the 2s subshell. The correct answer is 2, not 1 as mentioned in the answer.

What is the Aufbau principle?

• Electrons fill the lowest energy orbitals first

• Electrons fill the highest energy orbitals first

• Electrons fill orbitals randomly

• Electrons fill orbitals based on their spin

Answer explanation

The Aufbau principle is a fundamental concept in quantum mechanics that explains the arrangement of electrons in an atom. The correct answer is 'Electrons fill the lowest energy orbitals first'. This principle states that electrons occupy the lowest energy orbital available, before moving to higher energy orbitals. This is why the other options are incorrect.

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What are valence electrons?

• Electrons in the outermost energy level of an atom

• Electrons in the innermost energy level of an atom

• Electrons in the nucleus of an atom

• Electrons in the subshells of an atom

Answer explanation

Valence electrons are the electrons in the outermost energy level of an atom. They are significant because they are involved in the formation of chemical bonds with other atoms. The other options mentioned electrons in the innermost level, nucleus, and subshells, which are not correct as per the context of the question.

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What is the electron configuration of ions?

• The same as the electron configuration of neutral atoms

• Different from the electron configuration of neutral atoms

• Ions do not have electron configurations

• Ions have only one electron

Answer explanation

The electron configuration of ions is different from that of neutral atoms. This is because ions are atoms that have gained or lost electrons, thus altering their electron configuration. For instance, a neutral atom that loses an electron to become a positive ion will have a different electron configuration than it did before it lost the electron.

What is the electron configuration of the 3d transition metals?

• 3d¹⁰4s²

• 3d⁶4s²

• 3d⁵4s²

• 3d⁴4s²

Answer explanation

The electron configuration of the 3d transition metals varies, but the correct configuration for this question is 3d⁶4s². This configuration indicates that there are six electrons in the 3d orbital and two electrons in the 4s orbital. This is the typical electron configuration for many of the 3d transition metals.

Why is there no 1p electron configuration?

• There are no p orbitals in the first shell

• The first shell can only hold one electron

• The first shell does not have subshells

• The first shell is too small for p orbitals

Answer explanation

The reason there is no 1p electron configuration is because there are no p orbitals in the first shell. The first shell only contains s orbitals, which can hold up to two electrons. P orbitals are introduced in the second shell and beyond, allowing for more complex electron configurations.

Why does the electron configuration go from 2s to 2p instead of to 1p?

• The 1p subshell is not needed for the first shell

• The 1p subshell is higher in energy than the 2s subshell

• The 1p subshell does not exist

• The 1p subshell is unstable

Answer explanation

The electron configuration goes from 2s to 2p instead of to 1p because the 1p subshell is not needed for the first shell. The first shell only has the 1s subshell, which can hold up to 2 electrons. The 2s and 2p subshells are part of the second shell, which can accommodate more electrons.